System and apparatus for effecting a correction of deflection of strip steel from its normal path of travel in a tandem rolling mill



Jan. 27, 1970 TOSHIYUKI KAJIWARA SYSTEM AND APPARATUS FOR EFFECTING ACORRECTION OF UP STRIP STEEL FROM ITS NORMAL PATH OF TRAVE 1 IN A TANDEMROLLING MILL Filed Oct. 10. 1967 3,491,562 DEFLEC'IION INVENTOR UnitedStates Patent 3,491,562 SYSTEM AND APPARATUS FOR EFFECTING A CORRECTIONOF DEF LECTION 0F STRIP STEEL FROM ITS NORMAL PATH OF TRAVEL IN A TANDEMROLLING MILL Toshiyuki Kajiwara, Hitachi-shi, Japan, assignor toHitachi, Ltd., Tokyo, Japan, a corporation of Japan Filed Oct. 10, 1967,Ser. No. 674,235 Claims priority, application Japan, Oct. 12, 1966, 41/66,611 Int. Cl. B21b 37/04 U.S. Cl. 7212 6 Claims ABSTRACT OF THEDISCLOSURE System and apparatus for effecting a correction of deflectionof a strip from its normal path of travel in a tandem rolling mill inwhich deflection detection means provided at the outlet of each millstand gives an instruction signal to deflection correction means of theparticular rolling stand concerned and at the same time gives anecessary instruction signal to deflection correction means of thesucceeding mill stand so as to automatically steering the strip at thethreading thereof.

BACK-GROUND OF THE INVENTION Field of the invention This inventionrelates to a system and an apparatus for effecting a correction ofdeflection of a strip in a tandem rolling mill, particularly in a coldstrip mill, whereby deflection of the leading top portion of a stripfrom its normal path of travel can automatically be corrected.

Marked advances have been made in the art of tandem cold rollingoperations to develop a automatic production system of high productionrate. With the advent of high speed feeding operations, rolling speedamounts in some cases to over 2,000 meters (about 6,600 feet) perminute.

In a cold strip mill, rolling operations are performed for each coil ofa strip, so that upon completion of rolling of one coil the leading endof a strip of another coil should be successively fed to each millstand. This feeding operation is usually called threading of the strip.No established system has hitherto been available for automaticallycarrying out these threading operations. The main reason for this isthat it is very difllcult to quickly effect a correction or compensationfor deflection of strip from its normal straight line path of travel foreach mill stand. The top portion of strip which comes out of a millstand is not tensioned until it is bitten by work rolls of thesucceeding mill stand. Under these circumstances, the top portion ofstrip in many cases does not travel in a straight line to be alignedwith the center of roll path of the each succeeding mill stand but tendsto be deviated from its straight or normal path of travel. Conseqeuntly,the top of strip impinges on a side guide and the strip is preventedfrom entering between the Work rolls of the succeeding mill stand.

Present practice of strip rolling requires an operator to grip the topof a strip and force the same to move through a side guide. According tothis practice, operational efliciency is low and additional labor isrequired. Proposals have been made to effect a correction of deflectionof strip from its normal path of travel in conjunction with adjustmentof the screw down of work rolls. As subsequently to be described,however, it has been impossible to effect a full correction ofdeflection of strip from its normal path of travel according to theconventional technical concept.

Patented Jan. 27, 1970 The present invention has as its object theprovision of a system and an apparatus for completely effecting acorrection of deflection of strip from its normal path of travel.

BRIEF EXPLANATION OF THE DRAWINGS FIG. 1 is an explanatory view showingthe manner in which a strip is deflected from its normal path of travelin a tandem rolling mill;

FIG. 2 is a schematic view showing essential portions of a tandemrolling mill incorporating a system for correcting deflection of stripfrom its normal path of travel according to the invention; and

FIG. 3 is a view to explain the manner in which a strip travels in atandem rolling mill incorporating the system according to the presentinvention.

DESCRIPTION OF THE INVENTION Deflection of a strip from its normal pathof travel in a tandem rolling mill can be caused by various factors suchas lack of parallelism between upper and lower work rolls defining aroll gap therebetween, deviation of the strip in the roll path withrespect to the center of roll Width, irregular thickness distribution ofstrip in the transverse direction and the like. Of these factors, thelack of parallelism between upper and lower work rolls and the deviationof the strip in the roll path with respect to the center of roll widthhave been responsible in the majority of cases for deflection of thestrip from its normal path of travel. After being rolled, the striptends to be deflected about its top portion at a certain rate ofcurvature toward the side of the roll path on which the screw down rateis lower or in the direction in which the center of strip width isdeviated in the roll path with respect to the center of roll width. Thisphenomenon will be explained in detail with reference to FIG. 1.Assuming that the roll gap between work rolls 1, 1 is smaller on the Aside than on the B side that is; the screw down rate is higher on the Aside than on the B side, the portion of the strip on the A side isstretched a greater amount than the portion on the B side, causing thetop portion of strip to be curved as shown at a. If the top of stripwere left free, it would move in the direction d shown in imaginarylines and an amount of its deflection from the normal path of travelwould increase as it continues to proceed, making it impossible toeffect automatic strip threading. It is to be noted in this connectionthat if the roll gap between work rolls can be controlled in such amanner that the screw down rate of the work rolls 1, 1 is reduced on theA side and increased on the B side so 'as to bring about parallelismbetween the upper and lower work rolls, it will be possible to eflect acorrection of deflection of the strip from its normal path of travel. Inone method of correcting such deflection, deflection detection means 5,5' may be provided which detects an amount of deflection 6 and producesa signal in accordance with the amount detected. If the roll gap betweenthe work rolls is adjusted according to this signal, the strip willtravel as shown in a, b and 0, thereby bringing the amount of deflectionto 6 (Where 5 6 because it takes time to effect adjustments of a rollgap between rolls.) However, use of such correction means alone does notwarrant automatic strip threading. The reason is this, the constructionof a rolling mill is such that it is physically impossible to installdeflection detection means as close to the rolls 1, 1 as might bewished. Therefore, a correction of deflection of the strip cannot beeffected with respect to its forward top portion 1 If the strip with itsforward end portion deflected as described above is introduced into theroll path between the next following work rolls 2, 2' the forward topportion will be deviated from the roll path with respect to the centerof roll Width so that it is deflected a greater amount from its normalpath of travel as shown at e.

Control of deflection of a strip become complicated from the fact thatthere is no means provided to effect a correction of this deflectiontill the top of strip reaches the next following deflection detectionmeans 6, 6'. Accordingly, the amount of deflection of strip when itreaches 6 will be greater than 5 In the work roll 2', it is impossibleto effect a correction of deflection of strip while it is travelling forthe distance I. From the foregoing description, it will be understoodthat if the method described above is employed to effect control overdeviation of strip, the amount of deflection of strip will be increasedas it passes through each mill stand until at last the deflectionbecomes so great in amount that the strip cannot be admitted into thepath through a side guide 20, 20".

The present invention can obviate the problem of deflection of the topof a strip from its normal path of travel encountered during threadingin tandem rolling mills.

The invention is characterized by the provision of deflection detectionmeans at the outlet of each mill stand, which is adapted to give aninstruction signal to deflection correction means of the particular millstand concerned and at the same time give a necessary instruction signalto deflection correction means of the succeeding mill stand.

The invention will now be explained in detail with reference to FIGS. 2and 3. The tandem rolling mill shown in the drawings is illustrated ashaving only two mill stands. However, such rolling mill generally hasfour to six mill stands, and it is to be understood that the rest of thestands are omitted. A first mill stand includes work rolls 1, 1 andback-up rolls 3, 3, and a second mill stand includes work rolls 2, 2',and back-up rolls 4, 4'. Deflection detection means 5, 5 are disposedrearwardly of the first mill stand, while deflection detection means 6,6 are disposed rearwardly of the second mill stand. 7 is a strip to berolled. The back-up rolls of the first and second mill stands areprovided with bearing boxes 8 and 9, respectively. 10 and 11 are screwdown adjusting means for the first and second mill stands, respectively,which serve concurrently as deflection correction means in the presentinvention. Screw down electric motors 12, 12 are disposed on the A sideand on the B side respectively of the first rolling stand, while screwdown electric motors 13, 13' are mounted similarly on the A side and onthe B side, respectively, of the second rolling stand.

The deflection detection means 5 is provided with a transducer 14 whichprovides detected signals to control means 16, 17 for generatinginstruction signals. According to the instruction signals, respectivescrew down motors 12, 12' and 13, 13' of the first and second millstands are capable of adjusting amounts of screw down of the work rolls1, 1 and 2, 2. on the A side or the B side or both sides so as to steerthe strip, that is; to correct deflection of the strip from its normalpath of travel. The deflection detection means 5 may comprise a pair ofposition detectors disposed on the opposite sides of the predeterminedstraight line path as shown in the drawings. Position detectors may bethose detecting a change in electromagnetic fields, a change in lightbeams or a change in X-ray beams. The deflection detection means 6 isprovided with a transducer which is operatively connected to the screwdown motors 13, 13' of the second mill stand through control means 18 aswell as screw down motors of the next following rolling stand (notshown) through control means 19.

The operation of the present invention will now be explained Withreference to FIG. 3. Assuming that the top of strip travelling from thework rolls 1, 1 to the work rolls 2, 2' is deflected a certain amountfrom its normal path of travel to the B side of the rolls, thedeflection detection means 5 will detect the deviation and provide asignal through the transducer 14 corresponding to the amount ofdeflection to control means 16 which produces instruction signals to thescrew down motors 12, 12'. The instruction signal controls the motors soas to adjust the screw down rate of the work rolls 1 throu h the back-uprolls 3, 3' in such a manner that the roll gap therebetween is increasedon the A side and reduced on the B side. At the same time, a signal willbe also issued to the screw down motors 13, 13 of the second mill standthrough control means 17, which similarly adjust the roll gap betweenthe work rolls 2, 2' through the back-up rolls 4, 4' in such a mannerthat the screw down rate of work rolls 2 is made higher on the B sidethan on the A side. This causes the top of strip 7 to be stretched alarger amount on the B side than on the A side so that the top of stripcomes out from the rolls 2 in the manner as shown at 1. Then the topwill successively proceed in its path of travel in the manner shown at gand h. After passing through the phase h, the top of strip 7 would bedeviated to the opposite side as shown in imaginary lines j if it wereleft to follow its own course, since the stretching of strip 7 has bythen grown larger on the B side than on the A side. However, deflectionof strip 7 in the opposite direction has by then been detected by thedeflection detection means 6 so that the top of strip does not proceedin the manner as shown at j but travels straight as shown at i sinceadjustment of roll gap between the work rolls 2 are effected byactuation of the deflection detection means 6. If the strip weredeflected from its normal roll path between the rolls 2, a correction ofthe deflection could be effected in the same manner in cooperation withthe succeeding mill stand.

From the foregoing description, it will be appreciated that the presentinvention makes it possible to aut matically steer a strip at thethreading, that is, to automatically effect a correction of deflectionof the top of a simple device, thereby permitting to effect fullautomatic strip threading operations in a tandem rolling mill.

I claim:

1. A system for effecting a correction of deflection of a strip from itsnormal path of travel in a trandem rolling mill characterized in thatdeflection detection means provided at the outlet of each mill standgives an instruction signal to deflection correction means of theparticular mill stand concerned and at the same time also gives anecessary instruction signal to deflection correction means of thesucceeding mill stand to automatically effect a correction of deflectionof strip steel from its normal path of travel whereby deflection of thetop of the strip fed to a tandem rolling mill can automatically becorrected.

2. A system for effecting a correction of deflection of a strip from itsnormal path of travel in a rolling mill as claimed in claim 1 in whichsaid deflection detection means is operative to adjust the roll gapbetween upper and lower work rolls by varying the screw down rate onopposite sides of the rolls for effecting a correction of deflection ofthe strip from its normal path of travel.

3. A system for effecting a correction of deflection of strip steel fromits normal path of travel in a rolling mill as claimed in claim 1 inwhich said instruction signal 1s transmitted through a transducermounted in said deflection detection means to said deflection correctionmeans including screw down electric motors so as to adjust the roll gapbetween upper and lower work rolls for effecting a correction ofdeflection of the strip from its normal path of travel.

4. An apparatus for steering a strip at threading operation in a tandemrolling mill including at least first and second mill stands each havingscrew down mechanism to adjust the roll gap thereof wherein theimprovement comprises deflection detecting means provided at the outletof the first mill stand for providing a detected deflection signalaccording to a deflection of the strip from the predetermined paththereof and control means operatively coupled with the deflectiondetecting means and the respective screw down mechanisms of the firstand second mill stands for providing necessary screw down instructionsignals to the first and second mill stands according to the detecteddeflection signal so as to steer the strip.

5. An apparatus according to claim 4, in which said deflection detectingmeans comprises a pair of detectors disposed on the opposite sides ofthe predetermined path of the strip so as to produce a detected signalcorresponding to the deflection of the strip from the predeterminedpath.

6. An apparatus according to claim 4, in which said control meanscomprises first and second control means operatively connected to thescrew down mechanisms of the first and second mill stands, respectively,for providing most pertinent instruction signals to the first and secondmill stands, respectively.

References Cited UNITED STATES PATENTS MILTON S. MEHR, Primary ExaminerUS. Cl. X.R. 226-21

